liblight: Add battery light support

Change-Id: I4b73363545b71fbb435b9b577fdfff30d756b90c
hammerhead: Enable USB audio

Change-Id: I83861e0c70eeeb5035f89bfa4c32f19c21236437
hammerhead: Better USB audio support

 * Use new QCOM USB audio path which uses the AFE proxy.
 * This fixes the issues with skips and drops when UI sounds play.

Change-Id: I9941d49b669208959353805f43f51874a415eba3